A representative example of a rotating electrical machine effectively using a reluctance torque is a drive motor for a hybrid electric vehicle. At the low-speed rotation, the motor generates a large magnet torque by a strong rare-earth permanent magnet. At the time of high-speed rotation, the motor achieves high output by utilizing the reluctance torque while suppressing motor voltage by a weakening field.
A brushless electric motor having such functions is disclosed, including: a stator obtained by winding a distributed coil around a stator core formed by laminating electromagnetic steel sheets; and a rotor having a permanent magnet and a high-permeability magnetic member (auxiliary salient pole) (Japanese Patent No. 2,667,815 (Claim 1 and FIG. 1).
In the brushless electric motor, however, it is difficult to make the magnetic field distribution at the time of no load in the air gap have a sine wave shape, and the rotor has a complicated magnetic structure in the circumferential direction. Consequently, the electric motor generates electromagnetic exciting force in various modes. As a result, vibration and noise tend to occur in the motor. Since a wire is wound around the stator core obtained by laminating electromagnetic steel sheets, a coil end is inevitably formed and, due to the coil end, the axial length of the motor increases. Particularly, in a flat motor, the coil end hinders realization of miniaturization of the motor.
An object of the present invention is therefore to provide a claw-teeth-type rotating electric machine capable of realizing reduction in vibration and noise while utilizing reluctance torque.